Lubricant compositions exhibiting synergistic relief of metal fatigue

ABSTRACT

Lubricant compositions are provided containing, in an amount sufficient to improve metal-fatigue, a synergistic mixture of (a) isopropylaminoethanol and (b) a reaction product of an alkenyl succinic anhydride and a polyethylene amine.

United States Patent [1 1 Polk [111 3,859,221 1 1 Jan. 7, 1975 1 1LUBRICANT COMPOSITIONS EXHIBITING SYNERGISTlC RELIEF OF METAL FATIGUE[75] Inventor: Conrad J. Polk, Cranbury, NJ.

173] Assignee: Mobil Oil Corporation, New York,

[21] Appl. No.: 353,179

[521 US. Cl. 252/515 A, 252/515 R [51] Int. Cl Cl0m 1/32 [58] Field ofSearch 252/515 A, 51.5 R

[56] References Cited UNITED STATES PATENTS 3,219,666 11/1965 Norman eta1 252/515 A X 3,280,029 10/1966 Waldman ..252/49.5

Primary ExaminerDaniel E. Wyman Assistant ExaminerAndrew H. MetzAttorney, Agent, or Firm-Andrew L. Gaboriault; Raymond W. Barclay;Benjamin 1. Kaufman 571 1 ABSTRACT 10 Claims, No Drawings LUBRICANTCOMPOSITIONS EXHIBITING SYNERGISTIC RELIEF OF METAL FATIGUE BACKGROUNDOF THE INVENTION metal-fatigue, which, essentially, involves metaldeterioration due to the application of cyclic stresses in undergoinguse, as, for example, in rolling contact bearings. In order to induceanti-fatigue properties to the lubricating medium, and particularlywhere the lubricant is, to some extent, water-contaminated, variousadditives have heretofore been suggested as antifatigue agents. Suchadditives have not, however, been found sufficiently successful tojustify extensive commercial use as lubricant additives.

SUMMARY OF THE INVENTION It has now been found that highly superiorantifatigue properties can be exhibited by lubricant compositions, byincorporating therein minor amounts of a synergistic mixture of (a)isopropylaminoethanol and (b) a reaction product of an alkenyl succinicanhydride and a polyethylene amine.

Insofar as the lubricant medium, per se, is concerned, this may compriseany liquid hydrocarbon oil, in the form of either a mineral oil or asynthetic oil, or in the form of a grease in which any of theaforementioned oils are employed as a vehicle. In general, mineral oils,employed as the lubricant, or grease vehicle, may be of any suitablelubricating viscosity range, as, for example, from about 45 SSU at 100F.to about 6,000 SSU at 100F., and, preferably, from about 50 to about 250SSU at 210F. These oils may have viscosity indexes varying from belowzero to about 100 or higher. Viscosity indexes from about 70 to about 95are preferred. T he average molecular weights of these oils may rangefrom about 250 to about 800. Where the lubricant is to be employed inthe form of a grease, the lubricating oil is generally employed in anamount sufficient to balance the total grease composition, afteraccounting for the desired quantity of the thickening agent, and otheradditive components to be included in the grease formulation.

In instances where synthetic oils, or synthetic oils employed as thevehicle for the grease, are desired in preference to mineral oils, or incombination therewith, various compounds of this type may besuccessfully utilized. Typical synthetic vehicles includepolyisobutylene, polybutenes, hydrogenated polydecenes, polypropyleneglycol, polyethylene glycol, trimethylol propane esters, neopentyl andpentaerythritol esters, di(2-ethy1 hexyl) sebacate, di(2-ethylhexyl)adipate, di(butyl phthalate, fluorocarbons, silicate esters,silanes, esters of phosphorous-containing acids, liquid ureas, ferrocenederivatives, hydrogenated mineral oils, chain-type polyphenyls,siloxanes and silicones (polysiloxanes), alkyl-substituted diphenylethers typified by a butylsubstituted bis (p-phenoxy phenyl) ether,phenoxy phenylethers, etc.

Of particular importance, for the purpose of improving metal fatigue, isthe synergistic mixture of (a) isopropylaminoethanol and (b) a reactionproduct of an alkenyl succinic anhydride and a polyethylene amine. Ashereinafter described, even though component (a) and component (b)individually, are found to impart improved fatigue lifeto metal, thecombination of these two components, in a total amount no greater thanthat employed individually for each component, exhibits a synergisticeffect, by imparting a markedly increased benefit as far as anti-fatigueeffect is concerned, greater than that of the aforementioned components,individually, even though the total weight of the combination does notexceed that of components (a) and (b), individually.

Insofaras the isopropylaminoethanol (a) and the aforementioned reactionproduct (b) are concerned, these two components are found to besynergistic in all proportions. For most applications components (a) and(b) are generally employed in a mol ratio from about 1:4 to about 4:1.Insofar as component (b) is concerned, the alkenyl succinicanhydride'and the polyethylene amine are generally reacted in a molratio of about 2: 1'. In general, the synergistic mixture of component(a) and (b) may be incorporated in the lubricant in any amountsufficient to improve metal fatigue. For most applications thesynergistic mixture is employed in an amount from about .01 to about 10%and, preferably, in an amount from about 0.1 to about 2%, by weight, ofthe total weight of the lubricant composition.

Insofar as the components of the synergistic mixture are concerned,isopropylaminoethanol, i.e., component (a), is a known compoundand isdescribed in the literature, together with its method of preparation,for example, in U.S. Pat. No. 3,280,029. The aforementioned reactionproduct, i.e., component (b), is also known and'described in'theliterature, together with its method of preparation, for example, inU.S. Pat. Nos. 3,172,892 and 3,219,666.

DESCRIPTION OF SPECIFIC EMBODIMENTS In order to demonstrate theimprovement in metal antifatigue properties realized by employing theabovedescribed novel synergistic mixture of the present in'- vention,compared with that realized by employing components (a) and (b),individually, comparative data were obtained as shown in the examplesofthe following table. Insofar as theindividual components of thesynergistic mixture are concerned, the isopropylaminoethanol wasprepared in accordance with the procedure described in'theaforementioned U.S. Pat. No. 3,280,029; component (b) was prepared inaccordance with the procedure described in the aforementioned U.S. Pat.Nos. 3,172,892 and 3,219,666, in which 0.5 mol of each of components (a)and (b), making a total of 1 mol synergistic mixture, was employed.Insofar as component (b), employed in the following comparative data, isconcerned, this product was obtained by reacting 0.5 molofpolyisobutenyl succinic anhydride and 0.25 mol of tetraethylenepentamineat a temperature of C. until the evolution of water had ceased.

The data were obtained by means of the General Electric Rolling ContactFatigue tester. This equipment is widely accepted, in the art, as arolling contact fatigue tester. Data are obtained by loading two crowneddiscs against a cylindrical test specimen with the discs and specimenrotating at 12,500 rpm. The end of the test occurs when one or morepieces of metal break away from the specimen surface as a result ofmetal fatigue. The formation of such pits on the specimen surfaceresults in vibration of the apparatus which is sensed by a vibrationswitch incorporated in the instrument. The test is terminated when thevibration level exhibits a preset level set on the vibration sensor.

In the above test, at least six fatigue failures were obtained for eachlubricant formulation. The data were analyzed by Maximum Likelihoodstatistics to give the L life, L life, and Weibull slope of thepopulation. L life is defined to be that life (in stress cycles) which90% of the test specimens are expected to survive; L life is defined tobe that life which 50% of the test specimens are expected to survive.The Weibull slope is a statistical parameter which measures the degreeof spread of the data in a given population. In fatigue testing,improvements in specimen life are determined by increased values of theL and L life of a population relative to a reference fluid; thus in thedata presented herein, improved performance affected by the additivesindividually or in combination, is reflected by increased and L lifevalues. With the above test standards in view, the following data, asshown in the table, were obtained employing the above-describedequipment and employing identical test procedures under identical testconditions in each instance. Each test was conducted with M-50 steeldiscs and SAE 52100 steel test specimens (-63 Rockwell C hardness) at atest speed of 12,500 rpm and a Hertz load of 700,000 psi.

TABLE ence to preferred compositions and components therefore, it willbe understood, by those skilled in the art, that departure from thepreferred embodiments can be effectively made and are within the scopeof the specification.

1 claim:

1. A lubricant composition comprising a major proportion of a liquidhydrocarbon oil selected from the group consisting of mineral oils,synthetic oils and greases thereof, containing, in an amount sufficientto improve metal fatigue, a synergistic mixture of (a)isopropylaminoethanol and b an alkenyl succinimide of an alkenylsuccinic anhydride and a polyethylene amine, in a mol ratio of about 2:1and in a mol ratio of (a) to (b) from about 1:4 to about 4:1.

2. A lubricant composition as defined in claim 1 wherein saidcomposition comprises a mineral oil of lubricating viscosity in therange from about SSU at 100F. to about 6,000 SSU at 100F.

3. A lubricant composition as defined in claim 1 wherein saidcomposition comprises a mineral oil of lubricating viscosity in therange from about SSU at 210F. to about 250 SSU at 210F.

4. A lubricant composition as defined in claim 1 wherein saidsynergistic mixture is present in an amount from about 0.01 to about10%, by weight, of the total weight of the lubricant composition.

5. A lubricant composition as defined in claim 1 wherein saidsynergistic mixture is present in an amount from about 0.1 to about 2%,by weight, of the total weight of the lubricant composition.

6. A lubricant composition asdefined in claim 1 wherein said alkenylsuccinic anhydride is polyisobutenyl succinic anhydride.

G. E. Rolling Contact Fatigue Test Data* L Life L,,, Life L,, Test Oil(L...) Test on Total Example Lubricant Formulation (Cycles X 10) (CyclesX 10) (L,,,) Wet Oil (L Wet Oil Percent l SAE 20 mineral oil 3.46 7.20100% 100% 200% water 2 SAE 20 mineral oil 5.47 7.05 158% 98% 256% waterisopropy- .aminoethanol (lmol 1 3 SAE 20 mineral oil 4.70 9.82 136% 136%272% +water "reaction product (1 mol 4 SAE 20 mineral oil 5.10 11.84147% 164% 311% water isopropylaminoethanol (0.5 mol and reaction product(0.5 mol SAE 52100 steel specimens 12,500 rpm 700,000 psi nominal HertzStress "Reaction product of polyisobutenyl succinic anhydride andtetraethylenepentamine As will be apparent from the foregoing table, thetotal improvement in fatigue life of the treated oil over the base oilwas 56%, as shown in Example 2, where 0.5 mol of isopropylaminoethanolwas individually employed (200% of Example 1 versus 256% of Example 2).Where the test oil contained 0.5 mol of the above-describedpolyisobutenyl succinic anhydridetetraethylenepentamine reactionproduct, an improvement of 72% was obtained (Example 3). However, wherethe test oil contained 0.5 mol of isopropylaminoethanol and 0.5 mol ofthe aforementioned reaction product, an improvement of 1 l 1% wasobtained (Example 4), markedly indicative of a true synergistic effect.

While this invention has been described with refermine.

1. A LUBRICANT COMPOSITION COMPRISING A MAJOR PROPORTION OF A LIQUIDHYDROCARBON OIL SELECTED FROM THE GROUP CONSISTING OF MINERAL OILS,SYNTHETIC OILS AND GREASES THEREOF, CONTAINING, IN AN AMOUNT SUFFICIENTTO IMPROVE METAL FATIGUE, A SYNERGISTIC MIXTURE OF (A)ISOPROPYLAMINOETHANOL AND B AN ALKENYL SUCCINIME OF AN ALKENYL SUCCINICANHYDRIDE AND A POLYETHYLENE AMINE, IN A MOL RATIO OF ABOUT 2:1 AND IN AMOL RATIO OF (A) TO (B) FROM ABOUT 1:4 TO ABOUT 4:1.
 2. A lubricantcomposition as defined in claim 1 wherein said composition comprises amineral oil of lubricating viscosity in the range from about 45 SSU at100*F. to about 6,000 SSU at 100*F.
 3. A lubricant composition asdefined in claim 1 wherein said composition comprises a mineral oil oflubricating viscosity in the range from about 50 SSU at 210*F. to about250 SSU at 210* F.
 4. A lubricant composition as defined in claim 1wherein said synergistic mixture is present in an amount from about 0.01to about 10%, by weight, of the total weight of the lubricantcomposition.
 5. A lubricant composition as defined in claim 1 whereinsaid synergistic mixture is present in an amount from about 0.1 to about2%, by weight, of the total weight of the lubricant composition.
 6. Alubricant composition as defined in claim 1 wherein said alkenylsuccinic anhydride is polyisobutenyl succinic anhydride.
 7. A lubricantcomposition as defined in claim 1 wherein said polyethylene amine istetraethylenepentamine.
 8. A synergistic mixture of (a)isopropylaminoethanol and (b) an alkenyl succinimide of an alkenylsuccinic anhydride and a polyethylene amine, in a mol ratio of about 2:1and in a mol ratio of (a) to (b) from about 1:4 to about 4:1.
 9. Asynergistic mixture as defined in claim 8 wherein said alkenyl succinicanhydride is polyisobutenyl succinic anhydride.
 10. A synergisticmixture as defined in claim 8 wherein said polyethylene amine istetraethylenepentamine.